Realization of network for conducting transmission/reception between computers which handle various digital data is advancing.
Meanwhile, a large number of VTRs (Video Tape Recorders), which load a video cassette provided with a tape-shaped magnetic recording medium (hereinafter referred to as a magnetic tape as occasion may demand) to record image information and/or audio information onto the tape-shaped magnetic recording medium, and/or reproduce image information and/or audio information which have been recorded, are used in various fields because long time recording can be realized by using the tape-shaped magnetic recording medium, and the video cassette is removal medium and can be carried with ease.
Accordingly, transfer of image information and/or audio information to and from external unit is realized by making use of the above-described network so that VTRs can freely conduct transmission/reception of information within the magnetic tape. From this fact, their use purposes are greatly improved. For this reason, there has been a great demand for realization of network of VTR.
In response thereto, there is devised a technique of conducting transmission/reception of image information and/or audio information from VTR to external unit on the network, e.g., computer by using widely used protocol such as FTP (File Transfer Protocol), etc.
Since it is necessary for the purpose of transferring data to external unit on the network to constitute, as file, data to be transferred to conduct file management by file system, file system has been introduced into VTRs in which concept of file did not exist in the prior art because research of image information or audio information could be sufficiently made by visual sense or auditory sense of user.
In general, in the file system, data recorded on recording medium is constituted as file to collectively perform management of processing relating to file operation such as read processing, write processing, delete processing and/or updating processing for file on the basis of information such as file name, file size, file preparation date and file updating date, etc.
Moreover, in the file system in which management of files recorded on recording medium is conducted on the file basis as described above, management is ordinarily performed in the state where data recording area of the recording medium is divided into a record entry (RE) area where files are recorded and a Free Space List (FSL) area where no file is recorded.
In the file system, in the case where new file is prepared, whether or not space (empty) area exists in the Free Space List (FSL) area is first retrieved. In the file system, in the case where space (empty) area exists in the Free Space List (FSL) area, there is conducted such a processing as to register that area into the Record Entry (RE) area to prepare a new file, and to delete file from the Free Space List (FSL) area.
However, in the file system of information processing apparatus using tape medium as recording medium like VTR, since system data necessary for file management is written at the leading position of the tape medium, there is required an operation to necessarily rewind tape medium up to the leading position to read system data into memory, at the time of starting of the information processing apparatus, or immediately after removal medium is loaded into: the information processing apparatus in the case where tape medium is removal medium. For this reason, there is a problem that such operation is very troublesome.
Further, in the case, e.g., where the content of file is rewritten, there is required an operation to rewind the tape medium until the leading position to update system data, or to temporarily store system data to be updated into a non-volatile memory, etc. in the case where the tape medium is removal medium to rewind the tape at the time of taking out of the tape medium to write the data at a predetermined position. For this reason, there is a problem that such operation is very troublesome.
Further, since VTR can sequentially provide access to the magnetic tape in accordance with command input by user, in the case where file system as described above is provided, there is a possibility that read processing and/or write processing of data may be performed by sequential access, i.e., through path except for the file system so that data is newly written into the data area of the file recorded on the magnetic tape. As a result, there is a problem that the file data would be broken.
Furthermore, the data constituting a file of which the file system performs management have correlation to each other, and are not independent in ordinary state. Such data do not become significant independent data until they are caused to be unit of file. However, since image file consisting of image data has the configuration in which plural GOPs (Group of Pictures) which are information completed by themselves are collected, significant independent data would exist within the file even if data is not caused to be of file unit.
For example, in the case where image data are handled in broadcasting services, etc., image file in which data serving as material have been recorded for a long time period is first generated. Then, only images necessary for broadcasting are extracted from the material to further add other image data to the extracted image data to thereby prepare image file for broadcasting. That is, independent arbitrary image data is extracted from a predetermined image file, etc. thus to prepare new image file.
Meanwhile, in the case where a desired information is retrieved from information recorded on a magnetic tape, e.g., video information or audio information, Time Code (TC) information indicating recording time of the information recorded at a predetermined track provided in the longitudinal direction on the magnetic tape at the time of recording the information or Control signal (CTL) used for tape drive servo control is used.
For example, at VTRs, when user retrieves desired information from information recorded on the magnetic tape provided within a video cassette, the magnetic tape was caused to be run up to the position where the information has been recorded by making use of Time Code (TC) recorded along with the information to conduct retrieval.
However, Time Code (TC) to be recorded onto the magnetic tape is not information indicating absolute position, on the magnetic tape, of video information and/or audio information which have been recorded on the magnetic tape, but is information indicating relative position with recording start point of video information or audio information being as a reference such that starting point of Time Code (TC) can be changed by user.
Accordingly, since it frequently takes place that the same Time Codes (TCs) exist on the magnetic tape, there was a problem that it is very difficult to retrieve information that user desires from information which have been recorded on the magnetic tape by using only Time code (TC) information.
For this reason, user has ensured retrieval of a desired information based on Time Code (TC) information as described above by actually reproducing the magnetic tape to confirm the information retrieval by visual sense or auditory sense. However, information retrieval dependent upon visual sense or auditory sense of user is reliable, but results in the problem that such retrieval is so troublesome that it takes much time.